What kind of method can be used to better distinguish the quality of the radiator? Here it is recommended that you use the "half hour illuminance method", turn on the illuminance meter, fix the lamp in a position and shine at the illuminance meter, read the initial illuminance, such as 1000lx.
After half an hour to read the illuminance meter, in general, its illuminance will decrease, because the LED chip has a characteristic, with the increase of the junction temperature, its light output will reduce, then you can be pushed back by the illuminance to how high the junction temperature rises in the end.
Generally, half an hour if the illumination is reduced by 10% or less, it is qualified or even better; If the illumination drops by 20% in half an hour, then this is a bit of a problem; If the hot state illuminance drops by more than 20% than the cold state illuminance for half an hour, the junction temperature has basically exceeded the tolerance range of the chip, so it can basically be judged that the radiator is unqualified.
Heat dissipation is particularly important for leds, and the most critical is the junction temperature of the chip inside.
If you want to obtain accurate information, it is necessary to get the temperature and light output curve of the chip, which is not applicable to all LED, some manufacturers of LED chip light output unrelated to temperature, and even can withstand high temperature, in this special case, it is best to take a look at the manufacturer's product measured curve, but for most LED, This method is applicable.
